Inspiron 1764 Boot problems

Hello,

I got an wierd problem with mine Dell Inspiron 1764

The laptop wont boot from battery if he is powered off for an couple of hours. To boot I have to remove the battery and hold the power button for 20 sec. Then connect the battery and charger. And if i'm lucky he will boot hit an single hit on the power button.

Sometimes I have to repeat the above steps an couple of time to boot the laptop.

I have already run the hardware test from usb stick and non errors where found. 

Also usefull mayby once the laptop is powered on i can remove the charger and laptop will work fine on battery. The lifetime of the battery is almost 3h and 30 mins. 

I think the battery me be malfunctional or something.

Any ideas on how to fix this?